Following the monetary focus — the last exception has some parallel in contract law, the idea of specific performance and that some things can't be replaced by any monetary value because of their uniqueness.<p>So in the relationship example, it's not just "inertia", it's the value you have by virtue of your unique position in the situation, in terms of history etc. Similar arguments can be said of your parents or children: in some abstract sense you could imagine other children or parents you could evaluate the relative value of, but they are not actually your children or parents and so don't have that value.<p>It's an interesting issue because there's a point at which something leaves the realm of monetary (or more broadly, fungible value) considerations per se, and different rules start to apply.